1. Field of the Invention
The present invention relates to a cylinder block being cast with cylinder liner which is manufactured by casting a cylinder liner while covering the end-face, a method of manufacturing, and a casting cylinder liner used for the same method.
2. Description of the Related Art
A cylinder block of an engine has been formed by die casting using a light metal such as aluminum alloy. A cylinder block made of aluminum alloy has a defect in wear resistance. To overcome the defect, a cylinder liner is inserted into a cylinder requiring wear resistance. A cylinder liner having a cylindrical shape is made of cast iron, which is cast together with a cylinder block when it is formed by die-casting. For an example, there is a die-casting method disclosed in Jpn. Pat. Appln. KOKAI Publication No. 2000-64902.
In the disclosed method, as shown in FIG. 11 and FIG. 12, a cylinder block 2 made of aluminum alloy is cast so as to cover the whole cylinder liner 1 including the end-face 3 of a deck surface side by an aluminum alloy 4. This cylinder block called an overcasting type has been often used.
The cylinder block 2 of this type is usually cast by using molds 5a and 5b of a die-casting machine, to cover the end-face 3 of the cylinder head side by aluminum alloy 4, as shown in FIG. 13. After being cast, a half-finished cylinder block body 2a is machined to finish the cylinder diameter. The inside of the cylinder liner 1 is grinded by a hole machining tool 7 along the finished inside diameter dimension position α indicated by a chain line in FIG. 14, together with an upper side projected part 4a covering the cylinder head side end-face of the cylinder liner 1. For example, boring or honing is used for this machining. The cast cylinder block body 2a is performed a machining to finish the deck surface of the cylinder head. The deck surface is polished by a polishing tool 8 along the final deck surface position δ indicated by a chain line in FIG. 14. The cylinder block 2 is completed through these machining.
In the usual process of casting the cylinder liner 1, a shaft-shaped part 10 that projects downward from the upper mold 5a forming the deck surface side of the cylinder block 2 is inserted into the cylinder liner 1, as shown in FIG. 13. The end-face of the cylinder liner 1 opposite to the deck surface side is supported by a holder (not shown) that is formed in flat on the mold surface of the lower mold 5b forming the opposite side of the deck surface side. Thus, the cylinder liner 1 is held between the upper mold 5a and lower mold 5b. 
If the position of the inside of the cylinder liner 1 is the same as the position of the end of the upper side projected part 4a covering that end-face, there is no place to hold the cylinder liner 1. Namely, if the whole cylinder liner is to be housed in the cavity formed by the upper mold 5a and lower mold 5b, the cylinder liner cannot be held at a desired position in the upper mold 5a and lower mold 5b for die-casting.
Thus, the inside surface of the cylinder liner 1 used for the overcasting-type cylinder block 2 has the wall thickness projecting to the inside diameter side from the end of the upper side projected part 4a covering the end-face 3 of the deck surface side of the cylinder liner 1, as shown in FIG. 14. By using this liner, the cylinder liner 1 is held between the upper mold 5a and lower mold 5b. 
Concretely, as shown in FIG. 13 and FIG. 14, in the deck surface side of the cylinder liner l, the portion of the end-face 3 of the cylinder liner 1, which projects to the inside diameter side from the cavity part 12a forming the upper side projected part 4a is used as a mold contact part 13. In the whole cylinder liner 1, the mold contact part 13 is pressed by an annular holding part 14 formed thicker than the other parts at the base of the shaft-shaped part 10. As a result, the cylinder liner 1 is supported between the holding part 14 of the upper mold 5a and the holding part 11 of the lower mold 5b. Namely, the cylinder liner 1 held inside the upper mold 5a and lower mold 5b. 
As a result of the hole machining, such as boring or honing in the cylinder liner 1, a hole may be bored at a position displaced from the finished inside diameter dimension position α which is designed. As long as this displacement (a manufacturing error) is within the machining tolerance for a finished product (the dimensional tolerance for a finished liner hole), a certain wall thickness of the cylinder liner 1 is ensured. Therefore, it is no problem to regard the cylinder block 2 as a product completed as designed.
The inside surface of the cylinder liner 1 is machined together with the upper side projected part 4a covering the end-face 3 by boring or honing, as shown in FIG. 14. Therefore, a machined liner hole 23 cannot be judged from the outside as to whether its position is displaced, even if the hole machining position is displaced.
There is a liner projected type cylinder block, in which a cylinder liner is cast by projecting from a cylinder block. In a cylinder liner used for this type, the inside surface is finished close to the dimension of finished inside diameter in the primary machining process. As the inside surface is formed close to the finished dimension before machining, this cylinder liner can be immediately judged or whether the machining quality is good or bad when displacement exceeding the tolerance range occurs.
In contrast, for the over-casting type cylinder liner 1, a primary machined product that is large in the finished inside diameter dimension α to the inside surface before machining is used to ensure the mold contact part 13. Since this type of cylinder liner 1 is large in the machining margin to the finished dimension, it is possible to complete the hole machining while a displacement exceeding the finished dimensional tolerance is being generated. Thus, the cylinder liner 1 having an extremely thin wall thickness portion may exit in the completed cylinder block 2.